Re 85c:

Quoth E’Tallitnics:

No. The class feature that allows ritual casting specifically states spells of that class.
I don't think this answers the question that No Brains was asking. An Acolyte, for instance, is a creature that casts spells like a 1st-level cleric. The question was not whether the Acolyte can (by any means) cast non-cleric spells; the question was whether an Acolyte could cast a cleric spell as a ritual, provided that it met the conditions. For instance, if an Acolyte prepares Detect Magic, could it then cast that spell without using a spell slot, by spending a longer time on it?